Beaufort Scale

The Beaufort wind scale is a standard scale, running from force 0 for calm to force 12 hurricane and above for the description of
wind speed. Each value represents a specific range and classification of wind speeds with accompanying descriptions of the effects on surface features. It was originally developed as a system for estimating wind strengths without the use of instruments.

It was introduced in 1806 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war frigate of the period, and it was later modified to include descriptions of effects on land features as well. It is currently still in use for this same purpose as well as to tie together various components of weather (wind strength, sea state, observable effects) into a unified picture.

The Beaufort Scale (for use at sea)

FORCE

DESCRIPTION

SEA STATE

SPEED

knots

m/s

0

calm

like a mirror

<1

0.0-0.2

1

light air

ripples, no foam

1-3

0.3-1.5

2

light breeze

small wavelets, smooth crests with glassy appearance

4-6

1.6-3.3

3

gentle breeze

large wavelets, some crests break, some white horses

7-10

3.4-5.4

4

moderate breeze

small waves, frequent white horses

11-16

5.5-7.9

5

fresh breeze

moderate rather long waves, many white horses, some spray

17-21

8.0-10.7

6

strong breeze

some large waves, extensive white foam crests, some spray

22-27

10.8-13.8

7

near gale

sea heaped up, streaks of foam blowing with the wind

28-33

13.9-17.1

8

gale

fairly high and long waves, crests breaking into spindrift, blowing foam in prominent streaks